External beam radiation therapy (EBRT) is a commonly used method of treating many different types of cancers, including breast cancer. Implementation of EBRT generally involves generation of high energy x-ray beams by a linear accelerator, and delivery of those beams to a patient's tumor or target tissue site. With careful treatment planning, the goal of EBRT is to deposit the high energy x-rays in the area of the cancer (e.g., the tumor mass itself, or tissue margin thereof after resection) to destroy cancer cells, while minimizing damage to normal, surrounding tissues. EBRT may be performed before or after surgery to remove a cancerous tumor, to reduce tumor size prior to surgery, or to prevent the cancer from recurring after surgery.
The treatment planning process will typically include the use of a specialized computer to calculate the radiation dose that will be delivered to the patient's target site and surrounding normal tissue. As part of the process, the volume of the tumor or other areas that require treatment are determined and outlined on treatment planning images (e.g., from CT, MRI, ultrasound, and/or PET/CT images). Normal structures that should be avoided or considered in devising treatment may also be outlined. Using that information, a treatment plan that delivers an appropriate radiation dose while minimizing dose to surrounding normal tissues can be generated. In certain instances, the process may employ such techniques as three-dimensional conformal radiation therapy or intensity-modulated radiation therapy.
Fiducial markers are widely used in image-guided radiation therapies such as external beam radiation therapy to more accurately localize the area to be irradiated. The fiducial markers generally have different radiographic properties than that of the surrounding tissue, e.g., soft tissue, bone, etc., and thus can help to distinguish between the tissues when imaged. The fiducials may be implanted into tissue, into resection cavities (e.g., a lumpectomy cavity), or both. After a lumpectomy, it is not uncommon for a clear fluid (“seroma”) to build up in the space previously occupied by breast tissue and also in other regions of the breast. Due to tissue changes as a result of the surgery, the presence of seroma fluid on radiographic images often makes it difficult to accurately determine the volume of tissue needing treatment. Thus, to avoid undertreating the area, the treatment volume is generally overestimated, which subsequently leads to radiation damage of a larger amount of normal tissue.
Accordingly, it would be useful to have fiducial devices with improved marking capabilities. Specifically, improved devices and methods for marking surgically formed cavities would be beneficial. Fiducial devices being capable of temporary placement within these tissue cavities, and related methods, would also be beneficial.